Curtis,
Serious question, as I'm new to all-grain. If you do a 1hr mash @ 140F, does it do any good to mash later at a higher temp? I would have thought that all the starch would've been converted by that point.
The problem with mashing at 140 is that it's the low end of the beta amylase, extremely low for alpha amylase, at the low end of gelatinization for barley and too low for wheat.
That said, both alpha and beta will work at those temperature, but very slowly. You would have the added benefit of limit dextrinase(140-145F) working in that temperature range, helping produce and extremely fermentable wort. The biggest problem here being that alpha amylase is going to be working very very slowly, and without alpha providing substrate for beta to work on, beta doesn't have much to do as it will be working a bit faster. That said, 140 is a poor choice as it's slowing the 2 main players. 145 would be a better choice for a extremly fermentable wort as the limit dextrinase will still be working and alpha will speed up, and you'll be right in the middle of beta's optimum temperature. Do a 1.5hr mash at 145, and an iodine test at the end of that, if there's still starch left, let it go for another half hour.
As far as stepping to a higher temperature after an hour at 140, well it would be required if you're only doing an hour at 140. Like I said above, the 140F rest will produce very fermentable wort(but not likely not in an hour), then stepping up the temperature will denature the limit dextrinase and allow the beta and alpha to work more quickly. If you're just looking for a very fermentable wort you could just do a single infusion at 149-150 for an hour, and I think you would achieve what you are looking for.
Alternatively, I know there is a mash schedule that employs use of limit dextrinase to make super fermentable worts by mashing low (149-150) and then cooling the mash to 145 and adding some new grain for some limit dextrinase enzyme that has not been denatured.
All that said, here's some numbers on what different temperature will give you according to Briggs et al., 1981; Hind, 1950; Hopkins and Krause, 1947.
Highest extract (mainly starch conversion): 149-154.4
Fastest saccharification: 158
Highest yield of fermentable extract: 149
Highest percentage fermentability: 145.4